In Iceland a continuum growth in disability benefit is a fact as in many other countries. As a consequence assessment procedures and partial disability benefits have come under reconsideration (OECD, 2007). A report from the Prime ministry (2007) started this work in Iceland and marked the beginning of the Work ability assessment which is the main object of this thesis. The research question is: Is the new work ability assessment a useful tool in vocational rehabilitation and diability claims? Findings: The Work ability assessment is a comprehensive assessment of the individual ability to participate actively in the labor market from a physical, mental and social perspective. The development of the method was also done in accordance with the mostmodern definitions and understanding of work ability. In the developmental phase the author was inspired by and used tablished methods from other countries that have been shown to be useful. The author also developed the instruments in the Work ability assessment by the use of consensus that should guarantee a minimum of usefulness. Part of this consensus has been done in cooperation with international experts and international velopmental project.Experts in Iceland also agree that these instruments should be useful. I have tested some of these instruments and method in the research part and they seem to indicate that these methods and instruments are useful. I have asked (in interviews and surveys) medical doctors and the clients in my study, and they seem to agree that these methods are useful. All these taken together indicate that this could be a useful method. Conclusion: The Work ability assessment is a useful instrument in vocationalrehabilitation and disability claims. It serves the purpose both as an instrument and as a method and are in accordance with the most modern definitions and understanding of work ability. The instrument works in a systematic way to motivate and activate theindividual by stressing what he can do and by minimizing function loss and increase adaption with early intervention and vocational rehabilitation at the same time. The method itself is a continous process of information gathering in a structured way wherethe aim of the whole assessment process is to increase the individual´s work ability by exploring and trying all options from a comprehensive view. The information that is gathered in this process is valuable when it comes to choosing what options are in hand in vocational rehabilitation and on the decision on eligibility of disability benefit.